Oscar-winning actor Gene Hackman died of natural causes about a week after his wife Betsy Arakawa, who died after contracting a rare virus, a New Mexico medical investigator has said.

Hackman, 95, died at his Santa Fe home from coronary artery disease, with advanced Alzheimer’s disease a contributing factor.

Ms Arakawa, 65, died in the same house from hantavirus pulmonary syndrome (HPS), a respiratory illness caused by exposure to infected rodents. Her cause of death was listed as natural.

Authorities believe she passed away about seven days before her husband, to whom she had been married for more than 30 years. During his career, Hackman won two Academy Awards for The French Connection and Unforgiven.

It is likely that Ms Arakawa died first on 11 February, Dr Heather Jarrell of the New Mexico Medical Investigator’s Office, told a news conference on Friday.

She said it was “reasonable to conclude” that Hackman died on 18 February.

Ms Arakawa’s last known movements and correspondence were on 11 February, when she was seen going to a grocery store, a CVS pharmacy and a pet store, before returning home in the early evening.

Given that Hackman was in the advanced stages of Alzheimer’s disease it is “quite possible that he was not aware that she [his wife] was deceased”, said Dr Jarrell.

She told reporters she was “not aware of his normal daily functioning capability”.

Watch: Gene Hackman may not have known Betsy Arakawa was dead

Hackman had “significant heart disease, and ultimately that’s what resulted in his death”, Dr Jarrell said, adding that he had chronic high blood pressure.

He had not eaten anything recently, but showed no indications of dehydration, she added.

At the news conference, New Mexico Public Health Veterinarian Erin Phipps emphasised that hantavirus infections are extremely rare.

HPS is transmitted through contact with rodent droppings, urine or saliva, often when contaminated dust is inhaled.

She noted that 136 cases had been reported in the state over the past 50 years, and 42% resulted in fatalities.

Dr Phipps said evidence of rodent activity was found in some buildings on the property, though the risk inside the main house was considered “low”.

Investigators are trying to determine how Ms Arakawa contracted the illness. Hackman tested negative for hantavirus.

The couple were found in their home after neighbourhood security conducted a welfare check and saw their bodies on the ground through the window.

Gene Hackman reflects on career and acting

The remains were discovered in advanced stages of decomposition.

Hackman’s body was in a sideroom next to the kitchen, with a walking cane and a pair of sunglasses nearby, according to a search warrant affidavit.

Ms Arakawa’s body was in the bathroom, with scattered pills close to her.

Sheriff’s deputies found medication for thyroid and blood pressure treatment, along with pain reliever Tylenol, according to a court-filed inventory.

Citing privacy laws, authorities did not disclose who had been prescribed the drugs.

One of the couple’s three dogs was also found dead inside a crate near Ms Arakawa, while the other two dogs were alive.

The cause of death for the dog is yet to be determined, officials say. Dr Phipps told reporters that dogs do not get sick from hantavirus.

Initial investigations found no signs of forced entry or foul play at the couple’s $3.8m (£3m) home. Tests for carbon monoxide poisoning were negative, and no significant gas leaks were detected.

Hackman is survived by three adult children from his previous marriage.

Listen to the 911 call after two bodies found at Hackman residence

Hackman met Ms Arakawa when she was working part-time at a California gym in the mid-1980s, the New York Times has previously reported.

He won best actor Oscar for his role as Jimmy “Popeye” Doyle in William Friedkin’s 1971 thriller The French Connection, and another for best supporting actor for playing Little Bill Daggett in Clint Eastwood’s Western film Unforgiven in 1992.

A relative latecomer to Hollywood, Hackman’s breakthrough came in his thirties, when he was nominated for an Oscar for portraying Buck Barrow in 1967’s Bonnie and Clyde – opposite Warren Beatty and Faye Dunaway – and again for I Never Sang for My Father in 1970.

Both films saw him recognised in the supporting actor category. He was also nominated for best leading actor in 1988 for playing the FBI agent in Mississippi Burning.

He played more than 100 roles during his career, including supervillain Lex Luthor in the Christopher Reeve-starring Superman movies in the 1970s and 1980s.

Hackman featured opposite many other Hollywood heavyweights including Al Pacino in 1973’s Scarecrow and Gene Wilder in 1974’s Young Frankenstein.

His last big-screen appearance came as Monroe Cole in Welcome to Mooseport in 2004, after which he stepped back from Hollywood for a quieter life in New Mexico.